If you view a topic and click 'print view' from the topic tools drop down, when the print template loads, the bidi.css file is loaded - but doesn't need to be loaded for non RTL languages.

An if statement to load the bidi.css file could be used, just like the one in the overall_header.html and simple_header.html templates.

Template: viewtopic_print.html

Find:

<link href="{T_THEME_PATH}/bidi.css" rel="stylesheet">

Change To:

{% if S_CONTENT_DIRECTION eq 'rtl' %}

    <link href="{T_THEME_PATH}/bidi.css" rel="stylesheet">

{% endif %}